“I’m living on the edge,” admits Redwood Stephens, vice president of engineering for Synapse Product Development.

Sean MacLeod, president of Stratos Product Design, says his phone remains “unwrapped” even though “I go through one about every six months.”

Both designers say that while the idea of more active protection is intriguing, the challenges boil down to technology and money.

“It would clearly be competing with low-cost passive systems” like a plastic case or a rubber bumper, says Stephens, a mechanical engineer by training who has worked on Nike digital technology and other consumer electronics.

“ ‘I’ll be more careful’ —- that’s a fairly cheap solution,” agrees Mac­Leod, who has done projects for Apple and Microsoft, designed ruggedized laptops and worked on a lot of handheld electronics.

“When it gets down to it, cost is really such a brutal part of the consumer game.”

The patent, filed by Bezos and Amazon Vice President Gregory Hart in February 2010, involves using an air bag, springs or a jet of compressed gas to cushion a portable electronic device’s uncontrolled drop. There’s nothing in the patent’s broad descriptions to suggest Amazon, or anyone, has built such a system.

An automobile air bag seems almost simple by comparison. In a car there’s plenty of room for electronic and mechanical components. The added weight is minimal. The position of the person to be protected is fixed.

And while there’s not much time between the car hitting an obstacle and the rider hitting the dashboard, that 1/20th of a second is enough for the sensor at the front end to detect an impact and deploy the air bag inside.

Saving a phone or tablet computer, by contrast, first requires predicting a serious impact. As the patent explains, the system must determine that the device is falling, measure the distance to the approaching floor, calculate the crash velocity and then determine “whether the risk of damage to the cellphone … exceeds an acceptable threshold.”

To differentiate between dropping the phone on a shag rug and a driveway, the patent says the system might include a “surface-type detector … that may use a number of technologies, such as infrared, radar, X-ray or image recognition.”

Next, the “protection system” would kick in. That could require a “reorientation” element that rotates the device so it falls with the protected side down. This, says the patent, could use “gas expelled from a compressed gas cartridge” or a movable weight.

Finally, there’s the “protection element,” most intriguingly an air bag. Multiple air bags could be used to protect all sides of the device, the filing says.

Stephens says detecting a fall would not be difficult with the accelerometers, gyroscopes and other orientation systems now found in many smartphones. That’s the “lower-hanging fruit,” he says.

The next plausible step would be building a mechanism to “actively deploy mechanical bumpers, which are significantly lower cost than would be required for compressed gas,” he says.

But an air bag powered by compressed gas? “I could envision that getting bulky really quickly,” he says.

And some catlike mechanism to twist the falling device around so its cushioned side lands first? That seems like a tough nut to crack, Stephens says. “The question is how much weight do we have to throw around, or how much air do we have to blast, to accomplish that?”

MacLeod says miniaturizing the various components might be possible but expensive. “If it costs too much to actually develop the solution then it’s impractical from a business perspective.”

Still, he’s not ready to write off the mobile-phone air bag. “I wish I had one.”

There’s also an alternative approach to protection — insurance. One insurer of tech products, Asurion, reports that 53 percent of its claims last year were for damage, as opposed to loss, theft or malfunctions.

Whether it’s financial or physical protection, MacLeod says consumers may not pay much to protect the longevity of their devices “if you’re going to trade in every time there’s a new version, every six months.”

Of course, even if this Bezos patent goes nowhere, the man shares authorship on more than 70 others assigned to Amazon. Plus, he invented Amazon.

And even if this invention succeeds, there’s something air bags or springs won’t do: keep a phone dry and afloat when it’s dropped in the toilet.